Java程序员面试宝典笔记——第五、六章

绝地灬酷狼 2024-04-18 22:22 77阅读 0赞

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String不能修改。

StringBuilder后提出单线程，效率高，线程不安全。

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<table> 
 <tbody> 
  <tr> 
   <td>四类</td> 
   <td>八种</td> 
   <td>字节数</td> 
   <td>位数</td> 
   <td>数据表示范围</td> 
  </tr> 
  <tr> 
   <td colspan="1">整型</td> 
   <td>byte</td> 
   <td>1</td> 
   <td>8</td> 
   <td>-128~127（ - 2^7 ~ 2^7-1）</td> 
  </tr> 
  <tr> 
   <td>short</td> 
   <td>2</td> 
   <td>16</td> 
   <td>-32768～32767（ - 2^15 ~ 2^15-1）</td> 
  </tr> 
  <tr> 
   <td>int</td> 
   <td>4</td> 
   <td>32</td> 
   <td>-2147483648～2147483647（ - 2^31 ~ 2^31-1）</td> 
  </tr> 
  <tr> 
   <td>long</td> 
   <td>8</td> 
   <td>64</td> 
   <td>- 2^63 ～ 2^63-1</td> 
  </tr> 
  <tr> 
   <td colspan="1">浮点型</td> 
   <td>float</td> 
   <td>4</td> 
   <td>32</td> 
   <td>-3.403E38～3.403E38</td> 
  </tr> 
  <tr> 
   <td>double</td> 
   <td>8</td> 
   <td>64</td> 
   <td>-1.798E308～1.798E308</td> 
  </tr> 
  <tr> 
   <td>字符型</td> 
   <td>char</td> 
   <td>2</td> 
   <td>&nbsp;</td> 
   <td>表示一个字符，如('a'，'A'，'0'，'家')</td> 
  </tr> 
  <tr> 
   <td>布尔型</td> 
   <td>boolean</td> 
   <td>1</td> 
   <td>&nbsp;</td> 
   <td>true, false</td> 
  </tr> 
 </tbody> 
</table>

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